The Atlantic Seaboard is a watershed of North America along both

• the East Coast of the United States north of the Okeechobee Waterway &
• the Atlantic Canada (Maritimes) coast south of the Gulf of Saint Lawrence watershed.

The relatively narrow^[specify] continental area is demarcated on the south by drainage to the Okeechobee Waterway (which drains both westward to the Gulf and eastward to ocean), the Eastern Continental Divide (ECD) to the west, and the Saint Lawrence divide to the north, which extends to the Atlantic Ocean at Cape North (Nova Scotia peninsula). US physiographic regions of this watershed are the Atlantic Plain and the Appalachian Mountains & Highlands. Major sub-watersheds of the Atlantic Seaboard are the following (north-to-south):

Sub-watersheds adjacent to the Saint Lawrence divide (north-to-south)—

• Chedabucto Bay: 2,148 square miles (5,560 km²)[1] drainage area
• Gulf of Maine: 69,115 square miles (179,010 km²)
• Long Island Sound: 16,246 square miles (42,080 km²)^{[citation needed]}
• Lower New York Bay: >14,000 square miles (36,000 km²)^{[clarification needed]}

Other notable sub-watersheds—

• Delaware Bay: 14,119 square miles (36,570 km²)^{[clarification needed]}

— larger than several, but not adjacent to either divide

• Chesapeake Bay: 64,299 square miles (166,530 km²)

— adjacent to both divides (at the Triple Divide point)

Sub-watersheds adjacent to the Eastern Continental Divide—

• Albemarle Sound: >14,380 square miles (37,200 km²)[2]^[specify]
• Winyah Bay: >7,221 square miles (18,700 km²)[3]^[specify]
• Santee River: >4,531 square miles (11,740 km²)[4]^[specify]
• Savannah River: 9,850 square miles (25,500 km²)
• St. Johns River: 8,840 square miles (22,900 km²)
• Biscayne Bay: >2,800 square miles (7,300 km²)^{[clarification needed]}
• Kissimmee River: 3,000 square miles (7,800 km²)